1. Field of the Invention
The present invention relates to small internal combustion engines of the type used with lawnmowers, lawn tractors, other utility implements, and in sport vehicles, for example and, in particular, relates to speed control mechanisms for such engines.
2. Description of the Related Art
Small internal combustion engines typically include a carburetor which supplies an air/fuel mixture to one or more combustion chambers of the engine for combustion to drive the piston(s) and the crankshaft of the engine. The engine speed is typically regulated by a throttle valve disposed within the intake passage of the carburetor, which is movable between a substantially closed position corresponding to the engine being stopped or the engine running at a low or idle speed, and a substantially open position, corresponding to the engine running at its running speed.
Many small internal combustion engines also include a governor for maintaining a desired running speed of the engine, including a mechanical governor mechanism disposed within the crankcase and driven from the crankshaft. The governor mechanism may include one or more flyweights movable responsive to engine speed, which actuate a governor arm within the crankcase and a governor lever disposed externally of the crankcase. The governor lever is linked to the throttle valve of the carburetor. In operation, when the engine speed falls below a desired running speed, such as when a load is imposed upon the engine, the governor operates to further open the throttle valve of the carburetor to increase the engine speed. When the engine speed increases beyond a desired running speed, such as when a load is removed from the engine, the governor operates to further close the throttle valve of the carburetor to decrease the engine speed.
Many small internal combustion engines also include a speed control mechanism which is operable by an operator to set the running speed of the engine. The speed control mechanism includes a speed control lever which may be disposed either near the engine itself, or on the handle of an implement with which the engine is used. The speed control lever is movable between stop, idle, and various running speed positions, for example, to set the engine speed. When the speed control lever is disposed in the stop position, the throttle valve of the carburetor is substantially fully closed. When the speed control lever is disposed in the idle position, the throttle valve of the carburetor is slightly open to maintain a low engine running speed. When the speed control lever is moved through the various running speed positions toward a high speed position, the throttle valve is progressively opened to provide progressively higher engine running speeds. When the throttle lever is positioned to establish a desired running speed, that running speed is maintained by the governor responsive to engine load in the manner described above.
In small internal combustion engines that include a speed control mechanism, the speed control mechanism is typically oriented entirely in a substantially horizontal or a substantially vertical plane, wherein actuating movement of the speed control lever of the speed control mechanism occurs in the same plane. For example, the speed control lever for a horizontally mounted speed control mechanism is operable to adjust the speed control mechanism between stop, idle, and the various running speed positions by movement of the speed control lever in a substantially horizontal, side-to-side direction. Similarly, the speed control lever for a vertically mounted speed control mechanism is operable to adjust the speed control mechanism between stop, idle, and the various running speed positions by movement of the speed control lever in a substantially vertical, up-and-down direction.
One disadvantage of known speed control mechanisms is that the orientation of the speed control level is dictated by the orientation of the speed control mechanism. Often, a horizontally mounted speed control lever is desirable for applications such as go-karts, garden tillers, and other similar applications, while a vertical speed control lever orientation is desirable for snow throwers or other applications. Therefore, for different engine types, one speed control mechanism must be designed for mounting for horizontal, side-to-side actuation and a different speed control mechanism must be designed for vertical, up-and-down actuation, necessitating increased cost and increased total parts and inventory.
What is needed is a speed control mechanism for small internal combustion engines which is an improvement over the foregoing.